Approaches to Increasing the Adhesion Strength of Hard Wear-Resistant Nanostructured Coatings Based on the Ti–B–(Cr,Si, C)–N System

Protection of Metals and Physical Chemistry of Surfaces - The structure and properties of Ti–B–N, Ti–Cr–B–N and Ti–Si–B–C–N coatings, deposited...     

Multicomponent nanostructured films for various tribological applications

Many engineering materials working under severe cutting, stamping, or bearing conditions including humid and corrosive environments, as well as temperature fluctuation require a combination of chemical, mechanical, and tribological properties. For load-bearing metallic implants, the combination of excellent mechanical and tribological properties with biocompatibility and bioactivity is also of great importance. Desired properties can be achieved in hard films based on carbides, borides and nitrides of transition metals by alloying with metallic (Al, Cr, Zr) or nonmetallic (O, P, Si, Ca) elements. The present work demonstrates the potential of self-propagating high-temperature synthesis (SHS), magnetron sputtering (MS), and ion implantation assisted MS of SHS-composite targets to produce multicomponent nanostructured films with enhanced combination of properties. Three groups of recently developed films for mechanical engineering and medicine are considered: hard tribological Ti–(Al, Cr)–(Si, B, C, N) films with enhanced thermal stability, corrosion and oxidation resistance; nanocomposite and multilayered TiCrBN/WSe_x films with improved lubrication; and multifunctional bioactive nanostructured (Ti, Ta)–(Ca, Zr)–(C, N, O, Si, P) films (MuBiNaFs).     

Nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings for hard-alloy cutting tools

Nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings with various contents of chromium and nitrogen are obtained by the magnetron sputtering of multiphase composite targets. Their structure and phase composition are investigated by X-ray phase analysis, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and optical emission glow-discharge spectroscopy. The Ti-Cr-B-N and Ti-Cr-Si-C-N coatings are based on the fcc phase with texture (100) and crystallite size <25 nm. The Si₃N₄-based hexagonal phase was also revealed in the Ti-Cr-Si-C-N coatings. An investigation into the properties of coatings with the use of methods of nanoindentation, scratch testing, and by performing tribological tests showed that they have a hardness of up to 30 GPa, an adhesion strength no lower than 35 N, and their friction coefficient falls in the range of 0.35–0.57. Coatings also possess high thermal stability, resistance to oxidation, and corrosion stability in a 1N H₂SO₄ solution. The data obtained in tests of hard-alloy cutting tools indicate that the deposition of nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings increases its resistance by a factor of 11–17.     

Optimization of PVD Parameters for the Deposition of Ultrahard Ti–Si–B–N Coatings

Multicomponent Ti–Si–B–N coatings were deposited on high-speed steel (HSS) substrates by reactive magnetron sputtering using a SHS TiB + 20 wt% Si target. The influences of the substrate temperature, bias voltage, and nitrogen partial pressure on the structure and the elemental compositions of the films were studied. The films were characterized by high-resolution transmission electron microscopy (HRTEM), Auger spectroscopy (AES), and X-ray diffraction (XRD). The results of HRTEM analysis indicated the formation of an ordered–disordered structure with fine crystalline grains of hexagonal Ti(B,N) _x phase and amorphous integrain layers. The stoichiometry of the Ti(B,N) _x phase was strongly affected by PVD process parameters. The films were characterized in terms of their microhardness and wear resistance. The reasons for the high value of microhardness appear to be the result of stoichiometric phase composition, compressive residual stress, and dense and fine microstructure of the Ti–Si–B–N coatings. The tribological wear test results indicated the superior wear-resistant properties of Ti–Si–B–N coatings compared to TiN and Ti(C,N) coatings.     

Multifunctional nanostructured coatings: Formation,structure, and the uniformity of measuring their mechanical and tribological properties

The state of the art of the studies in the field of the development and certification of novel multifunctional nanostructured coatings having a wide spectrum of applications is reviewed. The main tendencies in the optimization of the compositions and properties of the coatings are described, and the modern methods of diagnostics of the nanostructured coatings are considered.     

Specificity of Measurements of the Hardness of Thin Functional Coatings Using Sclerometry,Micro- and Nanoindentation Methods

Protection of Metals and Physical Chemistry of Surfaces - Comparative analysis of sclerometry and micro-, and nanoindentation methods is performed for evaluation of hardness of thin multicomponent...     

Ta-doped multifunctional bioactive nanostructured films

Ta-doped multifunctional bioactive nanostructured films (MuBiNaFs) were deposited by DC magnetron sputtering or ion implantation assisted magnetron sputtering of composite (Ti,Ta)C + Ca₃(PO₄)₂ and (Ti,Ta)C + CaO targets produced by self-propagating high-temperature synthesis method. The films were characterized in terms of their structure, elemental and phase composition using X-ray diffraction, transmission electron microscopy, X-ray photoelectron, Raman, and IR spectroscopy. The films deposited in an Ar atmosphere consisted of (Ti,Ta)C, Ti_xO_y, and CaO phases in an amorphous matrix with P-O, C-O, and O-H bonding. In the films deposited in a gaseous mixture of Ar + 14%N₂, apart from the (Ti,Ta)(C,N), Ti_xO_y, and CaO phases, the indication of diamond-like carbon, bcc Ta and traces of P-O bonding were observed. The MuBiNaFs demonstrated high hardness in the range of 38-44  GPa, Young's modulus 310-350  GPa, high percentage of elastic recovery 70-75%, low friction coefficient down to 0.17-0.25 (both in air and under physiological solution) and two orders of magnitude lower wear rate compared with Ti substrate. Ti ion implantation of growing films was shown to be an effective instrument to decrease their high internal stress. Static water contact angle measurements indicated hydrophilic nature of film surfaces. The electrochemical tests demonstrated that the Ta-doped films had positive values of corrosion potential with low current density. In vitro studies showed that cultured IAR-2 epitheliocytes and MC3T3-E1 osteoblastic cells were well spread on the surface of films and their actin cytoskeleton was well organized. Osteoblastic cells had a high rate of proliferation on all examined films and expressed alkaline phosphatase activity, an early-stage differentiation marker. The MuBiNaF revealed a high level of biocompatibility and biostability at experiments in vivo.     

Synthesis and characterization of Ti-Si-C-N films

This study represents one of the first attempts to deposit multicomponent (more than three components) thin films by magnetron sputtering of multiphase composite targets (three phases or even more). Films of Ti-Si-C-N were synthesized through dc magnetron sputtering of xTiC+yTi₃SiC₂+zA composite targets (A was TiSi₂, SiC, or a mixture of these phases) in an argon atmosphere or in a gaseous mixture of argon and nitrogen. The as-deposited films were characterized using Auger electron spectroscopy, X-ray diffraction, transmission electron microscopy using selected area electron diffraction and high-resolution techniques, and microhardness. It was shown that the substrate temperature and the nitrogen concentration in the reactive gas had a strong influence on the structure and the composition of the as-deposited films. The films deposited from the Si-poor targets were either polycrystalline or contained a mixture of nanocrystalline and amorphous phases. An amorphous phase formed as individual grains rather than as intergrain amorphous layers. All films deposited from the Si-rich target were amorphous in nature. Particular attention has been paid to the atomic structure of grains and grain boundaries in the crystalline films. Polycrystalline grains contained a high density of dislocations and exhibited a curved appearance of the lattice fringes that is probably due to the presence of the long-range stress fields. The measurements of the lattice parameters using the selected area electron diffraction pattern (SA EDP) method indicated, with a high probability, that the polycrystalline grains consist of clusters of atoms with varying compositions. The grain boundaries in the nanocrystalline Ti-Si-C-N films had both ordered and disordered regions, although some regions close to the interface exhibited neither a fully crystalline nor a homogeneously amorphous structure. The atomic structure of an interface was shown to depend on the orientation relationship between adjacent grains. The atomic planes were perfectly matched when the two grains were oriented close to the [110] _fcc1//[110] _fcc2 zone axis. However, the interface dislocations were frequently observed at or near the grain boundary when [110] _fcc1//[001] _fcc2. The contribution of compressive stress as determined by an increase in the fcc lattice parameter is also discussed.     

Wear-resistant Ti-Al-Si-C-N coatings produced by magnetron sputtering of SHS targets

The results of an investigation into hard wear-resistant nanostructured coatings in the Ti-Al-Si-C-N system produced by the magnetron sputtering of multicomponent composite targets with various ratios of metallic and nonmetallic elements are presented. Coatings are deposited in the reaction gas mixture with constant values of the substrate temperature and bias voltage. The structure of coatings is investigated using X-ray diffraction, glow-discharge optical emission spectroscopy, scanning and transmission electron microscopy. The mechanical and tribological properties are determined using the nanoindentation and scratch-testing methods, as well as using tribological tests according to the “pin-on-disc” scheme. The results of investigations show that the coatings are based on the fcc phase consisted of titanium carbonitride with an average crystallite size of 2–20 nm; the crystallites are arranged in an amorphous matrix. The coatings of optimal composition possess hardness of 40–50 GPa, a stable friction coefficient of <0.55, an adhesion strength of ≥50 N, and a wear rate of <1 × 10^?5 mm³/(N m).